It is well known that major contaminants in engine exhausts from gasoline-powered vehicles are carbon monoxide (CO), hydrocarbons (HC), and oxides of nitrogen (NOx), and that the rates of such emissions draw certain curves, following fixed patterns, with changes in the air-fuel ratio of the mixture being fed to the engine.
Also known is the fact that NOx are difficult to remove from the exhaust whereas the elimination of CO and HC is relatively easy. Removal of NOx is theoretically possible if the engine is operated with fuel supply controlled within the range of air-fuel ratio where the NOx discharge is at a minimum. However, many knotty problems must be solved before the method is carried into practice.
What is believed a promising approach in the art today is some system using a triple-action catalyst which can eliminate NOx, CO, and HC all at once. When such a catalyst is employed, however, the air-fuel ratio of the mixture being fed to the engine must be restricted in a narrow range close to the theoretical air-fuel ratio. In order to keep the air-fuel ratio within the limited range, a feedback control quick to act is a necessity, but the quick action tends to cause oscillation and seriously affect the stability of the feedback system.
It is therefore an object of this invention to provide an air-fuel ratio controller which can restrict the air-fuel ratio of fuel supply to an internal-combustion engine within a narrow range as desired.
Another object of the invention is to provide an air-fuel ratio controller for an internal-combustion engine, including a feedback system stable in performance.
Yet another object of the invention is to provide an air-fuel ratio controller for an internal-combustion engine, including a feedback system capable of accurately controlling a proportional-action, solenoid-operated valve.
In accordance with the present invention, there is provided an air-fuel ratio controller equipped with a feedback system which detects the conditions of exhaust gases from an internal-combustion engine and controls the air-fuel ratio in reponse to the detected values so that the ratio can be maintained within a desired range, characterized by a compensating circuit incorporated in the controller for correcting the output of the detector to be linear at all times relative to the air-fuel ratio of the gaseous mixture. The arrangement stabilizes the performance of the feedback system and increases the speed at which the system responds and works.
These and other objects, advantages, and features of the invention will become apparent from the following description of embodiments with reference to the accompanying drawings.